Premises alarm systems generally allow technicians and others to use dial up or analog data modems over the PSTN to gain remote access to the equipment in order to modify the configuration and down load new firmware. Such an arrangement is illustrated in FIG. 9 which shows programming terminal 9.34 connected to the PSTN 9.13 via modem 935, and an alarm panel 9.02 connected to the PSTN 9.13 via a second modem 9.04.
A number of problems arise when attempts are made to transmit telephony signalling via a data network.
Some non-digital signalling systems utilize “real-time” or time-dependent information to convey signalling information. For example, in telephone signalling, a pause of a known duration can be used to indicate that the following information is to be interpreted in a different manner from that in which it would normally be interpreted. Similarly, a signalling burst can be “bracketed” between pauses of defined duration. We have found that this time dependent information can be lost or corrupted in transmission across data networks such as packet-switched networks. In particular, this information can be lost in transmission across an IP network.
Recent times have seen the rapid roll out of voice over IP (VoIP) services displacing the PSTN at customer premises. As legacy alarm systems are generally incompatible with VoIP services, new customer terminal equipment has been introduced to convert the signals from the legacy alarm panels' PSTN interface to a form compatible with IP networks used to deliver the VoIP service.
The introduction of customer terminal equipment blocks the path used to remotely down load configuration data and the like into alarm systems. Therefore in order to completely replace the PSTN with IP networks, the customer terminal equipment must provide the ability to remotely (and securely) modify the configuration of the alarm system over IP or cellular networks in a similar manner to the PSTN.
Some attempts have been made to solve this problem by providing VoIP functionality in the customer terminal equipment to support a PSTN like connexion to the premises alarm system so as to provide the communications path to remotely modify the configuration over IP. This approach suffers from a number of limitations, including poor security associated with using VoIP, and unpredictable channel quality. This is due to the fact that VoIP call quality depends on available bandwidth and other factors, such as jitter and packet loss affecting the IP path between the customer premises and the remote site from which the configuration is being carried out. If the bandwidth available over the IP path is low or is available in bursts, then the quality of the communications channel is poor and will not provide a reliable connexion for the analog data modems used to provide the data communications link for remote configuration.
This specification describes an arrangement which allows the secure remote configuration of alarm systems over IP or cellular links in a manner that is far less dependent on the quality of the communications path or the available bandwidth as it only uses the bandwidth specifically required for the data download, which could range from 110 bits per Second up to 33800 bits per Second, but not exceeding 64000 bits per Second.
The invention is also applicable to other legacy systems which have similar requirements.